Dynamic quantity sensors such as acceleration sensors or the like generally include a protection cap formed of resin, ceramic, silicon or the like on a sensor board having a movable portion for covering the movable portion and thereby protecting the movable portion of the sensor board (see Patent Document 1 (JP-A-10-253652), for example).
Furthermore, when a circuit board for transmitting/receiving electrical signals to/from a sensor board is combined with the sensor board and these boards are packaged by mold material such as resin or the like, a structure is adopted that generally includes a sensor board 10 having a protection cap CP fixed thereto and a circuit board 20 mounted on a lead frame 50 as shown in FIG. 19.
However, in this case, a plurality of boards 10, 20 are mounted on the flat plane, which causes the package body to be designed in a large size and need a protection cap CP. This accordingly leads to increased costs.
A structure has been proposed in which a sensor board having a movable portion and a circuit board are laminated together so that the movable portion is covered by the circuit board to thereby omitting the protection cap. Also, electrode bumps are formed on the circuit board so that the circuit board and the sensor board are connected to each other through the electrode bumps (see Patent Document 2 (JP-A-2001-227902), for example). In the laminate structure of the sensor board and the circuit board through the electrode bumps as described above, the sensor body can be miniaturized more than the case in which both the boards are mounted on the flat plane. However, there will still be a higher cost because it is necessary to form electrode bumps on the circuit board.